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There are definitely well documented and increasingly popular methods of treating a bevy of ailments and health conditions with medicinal marijuana. Smoking weed in such instances provides benefits (complete or partial treatment of various health issues) that outweigh any ill effects (smoke inhilation, etc.).

Your question however asks in the context of a chronic recreational smoker. Studies, including a recent exhaustive documentary by Dr. Sanjay Gupta showed that although novice smokers experience some of the adverse effects of being high, seasoned ones were able to do regular tasks such as driving equal to their non-medicated levels.

For those who believe it, marijuana can also aid in blood circulation, stress sensitivity as well as other emotional strains due to an increasingly relaxed state. There are no true links from smoking marijuana to lung cancer or any other form of cancer, nor do there appear to be adverse effects on the human brain or physiology.